Phase segregation assisted morphology sculpting : Growth of graphite and silicon crystals via vapor-solid reactions

Crystalline graphite and Si showing fertile morphologies are prepared via vapor−solid reaction growth (VSRG). By reacting CaC2 with vapors of CxCly (CxCly:  CCl4, C2Cl4, C4Cl6, and C5Cl6), porous, fibrous, and planar graphite were obtained at 973−1023, 1073−1123, and 1123−1223 K, respectively. Employing SiCl4 to react with MxSiy (MxSiy:  Mg2Si and CaSi2) generated many Si structures. These include clustered-particle and porous, wirelike, corallike, and planar or platelike at 1023, 1073, 1123, and 1223 K, respectively. The reaction products, the network solids (graphite and Si) and the ionic solids MCl2, phase-segregated into self-templating molds and casts and develop cooperatively into various three-dimensional structures. Final morphology of the network solids depends not only on the reaction temperature but their molar volume ratio to the MCl2 salt products.